Electric contact



Marcia 5', 1946 FJR. HENSEL 2,396,100

ELECTRIC CONTACT Filed June so, 1945 /ELECTRIC cowmcr FORMED OFGOLD BASE ALLOY CONTAINING LEAD OR THHLLIUM llrronNc-vs Patented Mar. 5, 1946 ELECTRIC CONTACT Franz It. Hensel, Indianapolis, Ind., asslgnor to P. R. Mallory & Co., Inc., Indianapolis, Ind., a corporation of Delaware Application June 30, 1943, Serial No. 492,917

3 Claims.

This invention relates to electric contacts. An object of the invention is to improve electric contact compositions.

The present invention contemplates an electric contact formed of a gold base alloy containins lead or thallium. s,

The contact alloys may contain:

. Per cent by weight Lead, thallium or lead and thallium 0.1 to 15 Gold or gold base alloys-.. Balance The gold used may be either pure gold or one of the carat golds. These consist of gold-base alloys containing additions of silver, copper or other metals such as nickel, zinc, palladium, platinum or manganese. A table or carat gold is given in Metals Handbook (American Society for Metals, Cleveland, Ohio) 1939 edition, page 1507. It is contemplated that silver or copper may be present in the metal composition from traces to 20%, and hence are sometimes present in proportions still higher than would be present if carat golds were used in making the compositions.

The preferred contact materials for most uses contain:

7 Per cent by weight Lead, thallium or lead and thallium 0.5 to 5 Gold Balance Examples of suitable specific contact materials are:

The contact alloys can be made by conventional alloying methods, as by melting the ingredients and thallium, balance gold.

FRANZ R. HENBEL.

v D. C. and A. C. circuits.

The alloys can also be made by powder etallurgical methods, consisting in mixing the powders, pressing same and then sintering them at a temperature where the ingredients diffuse into each other. In certain cases, it may be advisable to mix oxide powders of the lead and thallium with the gold base material and then carry out the sintering in a reducing atmosphere. In certain cases it may be advisable to retain a certain percentage of oxides in the alloy and for such applications the sintering may be carried out in a neutral or oxidizing atmosphere.

Contacts 01 the present invention find application in various electric devices, such as relays, voltage regulators, meters, gauges, telephone relays, thermostatic applications, sliding contacts and brush applications where certain anti-friction properties are required.

These contacts have-the advantages of tarnish resistance and thereby low contact resistance. They can be operated at low pressures both in The presence of lead and thallium in the percentages covered by the present invention, provides a finely distributed phase which, during the operation of the contacts, tends to form a non-wettingoxide'. The percentages of this oxide are so calculated that they will hardly afiect thecontact resistance but will greatly decrease the sticking tendencies of the contacts. Due to. the fact that the goldthallium and gold-lead systems are eutectic compositions, th metals lead and thallium are present in elementary form or metal compounds. The

distribution, therefore, of the non-wetting con-' stituent is microscopically fine. During the operation of the contacts, and particularly during the arc stage, a slight oxidationoi these microscopical particles prevents welding of the contacts because gold areas which might be momentarily fused will have no chance to flow together, thereby iorming a large enough molten pool to cause sticking.

While specific embodiments oi the invention have been described, it is intended to cover the 5 invention broadly within the spirit and scope or the appended claims.

What is claimed is:

1. An electric contact formed of a gold base alloy containing 0.1 to 15% of metal selected from the group consisting of lead and thallium.

2. An electric contact composed of 0.1 to 15% of metal selected irom the group consisting of lead and thallium, balance substantially all gold, said contact being characterized by low contact resistance and the presence of a finely distributed 3 phase formed predominantly of the lead or thallium capable of decreasing the sticking tendency of. the contact.

3. An electric contact composed of 0.5 to 5% of metal selected from the group consisting oi lead 

